1. Field of the Invention
The present invention relates to a liquid crystal display panel having a testing terminal for use in a prober check and a method of manufacturing the same.
2. Description of the Prior Art
Liquid crystal display devices have advantages that they are thin and light, can be driven with a low voltage, and consume little power, so that they have been widely used for various kinds of electronic appliances.
With regard to active matrix liquid crystal display devices in which an active element such as a thin film transistor (hereinafter referred to as TFT) is provided for each pixel, the ones which are excellent so as to be comparable to CRTs (Cathode-Ray Tube) in terms of display quality have been obtained, and used recently for a display in a portable television, a personal computer and the like.
A general TN (Twisted Nematic) type liquid crystal display device has a structure in which liquid crystal is sealed between two transparent substrates. Of two planes (opposite planes) of the transparent substrates opposite to each other, a common electrode (opposite electrode), a color filter, an alignment layer and the like are formed on one plane, and a TFT, a pixel electrode, an alignment layer and the like are formed on the other plane. Moreover, polarizers are adhered to planes reverse to the opposite planes of the transparent substrates, respectively. These two polarizers are disposed so that polarization axes of the polarizers are, for example, perpendicular to each other. According to such arrangement, the two polarizers allow light to transmit therethrough in a state where no voltage is applied, and become a mode to shield the light, that is, a normally white mode, in a state where a voltage is applied. Furthermore, when the polarization axes of the two polarizers are parallel with each other, the two polarizers become a normally black mode. Hereinafter, a substrate on which the TFT, the pixel electrode and the like are formed is referred to as a TFT substrate, and a substrate on which the common electrode, the color filter and the like are formed is referred to as a CF substrate.
The liquid crystal display devices have been recently required to possess far better capability. Particularly, improvement of a viewing angle characteristic and an increase in display quality has been strongly demanded. A vertically aligned (VA) type liquid crystal display device has been taken a hopeful view as the ones satisfying such demands.
Incidentally, in the manufacturing process of a liquid crystal display panel, when a first wiring layer (gate bus line and the like) is formed, short-circuits, abnormalities of resistance values or the like may occur due to excess or shortage of etching in some cases. In the case where such defects occur, since it is useless to execute post-steps, a prober check is performed after forming the first wiring layer to select defective products.
The present inventor thinks that the following problems will occur when high-definition of the liquid crystal display panel is progressed.
In the prober check, a testing pin is made to contact a testing terminal, thus existence of malfunctions of short-circuits and advisability of the resistance values are checked. However, a sharp testing pin has come to be used accompanied with the high-definition of the liquid crystal display panel. Therefore, in some cases, a part of the testing terminal may be peeled off due to the contact thereof to the testing pin to bring a state where a conductive foreign substance is adhered to the testing terminal.
In the case where the TFT substrate is manufactured and joined to the CF substrate while this conductive foreign substance remaining on the testing terminal, the conductive foreign substance and the common electrode on the CF substrate contact to each other to cause short-circuit defects. An alignment layer that is made of polyimide or the like is formed on the common electrode. Since the alignment layer is extremely thin in general, the alignment layer is readily cut when the conductive foreign substance contacts thereto. Thus, the testing terminal and the common electrode are electrically connected to each other through the conductive foreign substance.
The object of the present invention is to provide a liquid crystal display panel capable of avoiding a short-circuit between a testing terminal and a common electrode even if a conductive foreign substance is adhered to the testing terminal.
A liquid crystal display panel of the present invention comprises: a first substrate having a plurality of pixel electrodes, a plurality of gate bus lines, a plurality of data bus lines, a display portion in which a thin film transistor connected to the pixel electrodes, the gate bus lines and the data bus lines is provided, and the first substrate having a testing terminal which is disposed in a non-display portion around the display portion and connected to the gate bus lines; a second substrate having a common electrode disposed so as to be opposite to the plurality of pixel electrodes; and liquid crystal sealed between the first and second substrates, in which the common electrode is not formed in a region of the second substrate, which is opposite to the testing terminal.
In the present invention, a common electrode is not formed on a region of a second substrate (CF substrate) opposite to a testing terminal of a first substrate. Thus, even if a conductive foreign substance adheres to the testing terminal in a prober check and the conductive foreign substance is not removed in subsequent steps, an electrical short-circuit with the common electrode is prevented.
Furthermore, an insulating film may be formed on the region of the second substrate opposite to the testing terminal. Thus, the conductive foreign substance adhered to the testing terminal is contained by the insulating film, a contact of the foreign substance with the common electrode can be avoided. The insulating film can be easily formed by use of, for example, photoresist. In the VA type liquid crystal display panel, a projection for domain regulation is sometimes formed by use of photoresist. In this case, the insulating film can be simultaneously formed by use of the photoresist for forming the domain regulation projection.